Perfect for building the AR pistol you have always wanted!These nitrided steel barrels are chambered in 5.56mm NATO with a 1/7 right hand twist rate.Barrels feature M4 style feed ramps and a 1/2x28 TPI threaded muzzle.At 11.5" long (12 inch measured muzzle to back edge of the barrel extension) these barrels will accept any standard .750" gas block.Gas port hole is drilled 0.076".